Analysis of Unsymmetrical Faults in High Voltage Power Systems With Superconducting Fault Current Limiters

An analysis of unsymmetrical faults for a 110 kV sub-grid coupling with a superconducting fault current limiter is conducted in this contribution. For the design of the super-conducting fault current limiters it is essential to identify the highest possible voltage during the limitation process. As reference the symmetric three phase fault which generally leads to the highest short-circuit currents is used. Unsymmetrical faults like single line-to-ground fault, line-to-line fault and double line-to-ground fault are investigated in dependence of the superconducting fault current limiter impedance. The analysis shows that the double line-to-ground fault leads to the highest voltage drop during the limitation in the relevant range of impedance. Consequently, this fault is a crucial factor for the design of the superconducting fault current limiter.